Kerala-itinerary

Hello,

I'm going for a 13 day trip to Kerala. I would like to visit Varkala, Periyar, Munnar, Alleppey, Cochi and maybe Madurai. But I could need some advice which order I should visit these places? Starting point Varkala, ending point Cochi. First I was thinking of starting with the tourist ferry from Kollam to Alleppey, stay there for a night or twowith further tours into the backwaters, then go to Periyar and Munnar and finally to Cochi. But now I'm starting to doubt this plan.. Because maybe it's better to go directly from Varkala to Periyar? Or ? And it's now I also have begun to consider Madurai.. First of all; is there time for it? If there is, where in the itinerary should I put it? I don't want to rush through these 2 weeks though.

Thank you very much in advance.

Regards